Apparatus for testing the brakes of a motor vehicle



March 26, 1935; E. PIQUEREZ 1,995,578

APPARATUS FOR TESTING THE BRAKES OF A MOTOR VEHICLE Filed Aug. '7, 1950 4 s s 1 V i W I755 HRZUK l March'26, 1935.

E. PIQUEREZ v APPARATUS FOR TESTING THE BRAKES OF A MOTOR VEHICLE Filed Aug. '7, 1930 4 Sheets-Sheet 2 rllk A Fig.4

March 26, 1935.

E. PIQUEREZ APPARATUS FOR TESTING THE BRAKES OF A MOTOR VEHICLE Filed Aug. 7, 1950 4 Sheets-Sheet s Mental: m G fi E. PIQUEREZ March 26, 1935.

APPARATUS FOR TESTING THE BRAKES OF A MOTOR VEHICLE 4 Sheets-Sheet all llllllllllllllll ll .lzlllll. IIAIII Filed Aug. 7, 1930 termine for a given value of the stress .upon the Supposing now thatv the platfotm is loaded Patented Mar. 26,1935 7 f V a 1 UNITED STATES PATENT OFFIQE a 'u1',995,5 78 APPaaAT s FOR-TESTING THE BRAKES 0E Y A MOTOR VEHICLE Emile Piquerez, Paris, France Application ail-gust v; 1930; Serial No. 473570 I In FranceDecember 13, 1929 Claims; (61; 73-51) My invention relates to an apparatus u sed for friction'will be: qi=w:tan a. The three vectors testing the brakes of motor vehiclesu I It, is of extending from the origin into the second, and the greatest importance forsafety to determine third quadrants. rep-resent, (l) the downward the eiiiciency of the brake-s ot" a motorvehicle. force c'aused'by the weight ofra'vehicle wheel (w);

value of thetorque C necessary tobe applied to ing to cause a movement down the'said' plane; the wheel in order to rotate it when the brake is and (3) the force equal and opposite. to the applied in certain conditions. ,IfR indicates the horizontal. force necessary to prevent the wheel spoke of the wheel considered-rigiiF the force from moving down the inclined plane (it) As atlthe rim, the torque C;=RF it willbe-sufficient the angle opposite this vector having its sides 10 tQjHlfifiSllIESfiidfO-YCSF (which will be called the perpendicular to the sides of the angle a is braking force) in order. to appreciate the efiiequal to the angle a, the equation =Vw tan ot'may ciency of the brake. In effect considering a be derived. The whole platform will beinequiwheel loaded with a total; weight p,.the highestlibrium, if =2=2 a; tan a=1rtan In other value, that the force 1? may acquire when the words, the horizontally directed: force necessary frictional coefficient ofthe Wheel upon the ground to'movethe weight of; one roller to up an incline will be Fm fp, m sig a ing t e maximum of the-grade represented by the angle on will be,' of force F, beyond this value the wheel begins'to the weight of the, roller (w) times, the length skid and the braking is no longer eificientr Conof the grade dividedby the rise for a given length, sequently it will besufiicientin practice to; de-- (tan a).

driving element of the brake the fraction of with a, hee1 d to be tested whichis suitably charge K that the force- F0 must reachatv the b k d upon. it i l d. th t p indicates the wheel rim: Fo :Kp. When the amount. F1 of the weight up'qnsaid wheel; When a horizontal v force to be applied to'the rim ofeach oneof the tr F'i. ,a 1i d tp-thewheelaxle, supposing it Wheels in order to rotate it isthen measured in t be smaller than the adherence force of the predetermined conditions a 'of action upon the wheel rim tothe platform,- said force will be driving n bit Will y; e iln transmittedto the'platform'andkeep'it balanced der to obtain the optimum braking eifectto a'dupon th slope if; F1=(7r+p) tan a. V just e brakes. in 511611 a manneythat t e v lu Consequently it will only benecessar-yto modify of Frbe equal tothat of F0 which it was aimed to th zangie fbr 1 to-acquire the value F0 of the reach. q i V 1 optimumbrakingpower atthe instantwhen the Various ap a ha e dy-beenpmp d' wheel begins; to rotate around its axle. Fo Kp o obtain-said ltbu i allof them it j e beingthe value imposed for Fm-if this value is car- This efi'ciency is appreciated by measuring. the (2) theforce parallellto the-inclinediplanetend 5 w to first determine the u s r in Order ried-inthe equation ot equilibrium there will be as to deduct the optimum braking power Fa. H d; r

The apparatus according to the present inven- 7' K tion doesawaywith this previous valuationas a i i a it allows of directly measuring the braking. fracl-f qe tion K1 for every wheel on the vehicle. The ad- 1 1 7r 4o justment of the-brakes then consists in bringing it K: tan a-ltanf a said value K1 measured by the apparatus to the f I optimum value K which it isproposed to reach. Now in normal testing circumstances, tan of Considering a horizontal platform a. (Fig. 1)' the angle of the incline has a value included besupported by means of four rollers b upon. two t'WeenOA and 0.6 and the ratio 3 V inclined rectilinear rails c formingWitl'ithe-horh I V 7r zcntal an angle cc, will designate the horizontal 7 force to be exerted upon the platform to-maintain z it in-equilibrium. may vary from 0.10' to 0.15, the second term- 49, 5 .5 1% applied to each one of therollers, 15% of the value of the first term, this showing the weight 77 of the platform being similarly dein practice an error inferior-to the'testing errors; ccmposedin four. charges upon each roller-o1, 002', the first term gives therefore-a," very satisfying apor. The equation-ofequilibrium of anyone of proximation of the calculated value" of the cmthe rollers. (Fig. 2) noaccountbeing taken of the ciencyv coefficient K. 5

, The force may be decomposed infouh parts therefore indicates a rectification of from lotto O Consequently according to my invention the vehicle to be tested is placed upon four identical ing is determined.

In order to automatically produce this value the rolli g path of every roller has'a curvilinear shape the tangent of which slopes more and more as the roller moves forwards. As soon as the value of the coeflicient of efficiency is attained the carriage stops and this is indicated by a suitany desired point and is connected to the carriage by any suitable driving gear. All indexes are assembled upon a single board thus allowing to note at once which wheel begins to rotate owing to inadequate braking, the corresponding index remaining stationary and the others moving on. The board is preferably graduated in values of the coefficient of efiiciency of the brakes.

The apparatus may also be arranged in'such a manner that the vehicle is kept stationary and the tractive power is exerted uponthe lower part of the apparatus that is tosay upon the frame which will then be provided with means allowing it to move without friction. Lastly; in order to allow of eliminating the correcting term in the expression of K, the carriage may be balanced by counterweights or the like capable of returning them to the inoperative position at the top of their curvilinear path. In that case the carriages being first locked and the vehicle to which thebrakes have been applied being made completelystationary, the measuring operation tan a will be automatically startedby the unlocking of the carriages, the reading they stop.

Figs. 3 to 8 of the appended drawings show by way of example a mode of construction of an apparatus for testing the brakes of a motor vehicle according to my invention. I

Figs. 3 and 3a are partial longitudinal views of same the post which carries the'indicating board being omitted.

A Figs. 4 and 4a are partial plan views'of same.

Figs. 5 and 6 are respectively a. front elevation and a side view of the indicating board.

- Fig. 7 is a side View of the aforesaid post.

Fig. 8 is a diagram showing'a-certain number of values of the angle or, according to the stopping points of a roller upon its curvilinear rolling path.

Fig. 9 is a diagrammatic side view of a modified embodiment of the invention in which the automobile is held stationary during the test.

As will be seen in the drawings the apparatus comprises four carriages 1 1 ,"1, 1 having an taking place when appropriate surface capable of producing an ad-.

hesion equal at least to that of the average dry road-bed, which are placed in such a manner as tobe capable of supporting the four wheels At the front and in the middle of said frame are placed two small brackets 8 symmetrically to the axis carrying a transverse bar 9 which con stitutes the front pivot for two connecting rods 10. The latter being connected on the other hand at the back with a cylinder 11 which constitutes the driving means for the apparatus. A piston 12 contained within said cylinder is moved in same by air pressure from a small compressor 13 connected with said cylinder by means of a pipe 14. The rod 15 of piston 12 terminates outside the cylinder in a hook 16 to which the vehicle ably arranged index, which may be located at V whose brakes are to be tested is connected by any appropriate means.

The compressor13 is supported upon a foundation plate 17 placed at the front and on the sidesofthe apparatus it is covered over by a casing 18. 'Said plate 17 carries a post 19 at the top of which is placed an indicating board T. Flexible cables 209 20*, 20, 20 extend from the carriages 1 ,'1 ,.1 ,.1 pass through tubes 21, 21 21, 21 and'end at the indicating board T shown in detail in Figs. 5 and 6.

The board T is constituted by a box provided at the front with a glass 23 and inside with a sheet metalpartition 24 having four vertical slots 25. In each of the latter is guided the stem 26 of rectangular section of a semi-cylindrical index 26, which passes through the bottom of the box and is slidable in a tube 2'7. The ends of the cables 20*, 20 20, 20 are connected with the various indicators 26. The guides 27 are locked upon a small plate 28 by means of nuts and caps 29 the. latter comprising screwthreaded sockets upon which screw the'ends of the rigid tubular sheaths 21 .21 21, 21 for the various cables.

Springs'30 which are compressed when the carriages are not in operation are placed inside the guiding parts 27 and under the plunger-indexes, the indexes are then in their lowermost position. A fourfold graduation inscibed upon the glass of the board in parallel with the indexesindicates the values of the coeflicient of efficiency of the brakes for each wheel. It may be designed in function of the tangents of the angles on formed by the tangents at the various points of the bends 6 to the horizontal as shown in Fig. 8.

The mode of operation is as follows:

The vehicle being supported upon the four carriages "or platforms is connected by its fore axle to the hook 16 of the tractive piston. The compressor being started the driver operates the footlever of the brake so as to cause it to move to a predetermined position. This operation may be effected by any suitable mechanical device such for example as a screw jack. By reason' of the adhesion of the wheels upon the carriages the latter start forward. This forward movement loosens the cables 20 and the indica tors 26 are drawn consequently upwards by the springs 30. When one of the four wheels begins to rotate it will be ascertained by noting that the corresponding index remains stationary on the indicating board. It will then be sufficient to act upon the regulation of said wheel in order to make the braking eflicient thus preventing the subsequent unlevelling of the three remaining carriages relatively to the one which is stationary from producing a difference in the distribution of the weight among the four wheels and consequentlycausing a mistake in the readmg. o

' It will be notedthat it is possible to give to the brakes .of the same axle a coefficient of efficiency different from that given to those of the other axle-L Thus for example ifathe back wheels begin to'ro'ta'te, thecarr iages men-raining stationa1y;gand the 'front carriages move fur-' ther, the longitudi'nal inclination of the"'carriage still'beveryslight and will not-modify the distribution of the two axles. 7

Consequently my apparatus allows of strictly insuring thesan'fe braking-'efiici'ency tcrbothitl-ie wheels of the same aile wlfile-giving =a presto-tex mined preponderance ofoperatfon relatively to the other axle. i

A slight braking 'prepondera nce is generally allowedto the front-axle. Wl-ienthe' four carriages stop thevalues of -the =coeflici ents or e'fficiency for bothaxl'e's will be readable -on'the board 'I'.- When theseyalues arenot satisfactory the four brakes will regulated-in -suc'h a V manner that thefdesired K-valuescorrespond to the new positions of stoppage It is understood that'thiebonstruct'ionof the apparatus which has been described and illust-rated is by no means limitativethat for examplethe' construction of {the board T may vary and that similar indicating devices may be substituted to the-indexes; It will alsob'e eviderit-that the-cables; 20 may be mounted in such a manner as to pull upon the index'esfth'e'springsBll-being in that case-unbent when th'eindexes are at rest.

It will al-so be'understood that the apparatus may be arrangedso as to allow-of" the vehicle being locked in position. The tractive force would then; be applied to the lower part of the apparatus that is to-the whole of the rails sand of the longitudinal bearers"? ,whichirr'that case would be suitably arranged so as to move-without friction relatively to the ground;

The apparatus may also be devisedin such a manner that the carriages-are normally returned by any suitable system of ccunter'weights or springs 30 to the highest point of the rolling inclined path and may belocked in this position by connection 31 to a stationary part of the apparatus 32; The vehicle would thus be brought upon the carriages and suitably retained in position by connecting it for example to a stationary part 32 of the apparatus. The brakesbeing then applied to the desired extent it will only be'necessary to simultaneouslyfree the four carriages in order to allow themofrunning down their in-- clined paths causing therotationof the wheels up to the, moment when equilibrium is obtained I between the braking stress and the horizontal component of the power which tends to return the carriages at the bottom of their'rollingfpaths. At the instant when the equilibrium obtains the above indicated equations are realized and the of the fundamental equation of the apparatus.

Lastly, it will be observed that according to the first method herein described the coefficient ofefiiciency K which has been measured corresponds to the friction coefficient at .rest between the-partsand the brake drums. On: the contrary the second method the measured coefficient corresponds to the friction coeflicien't when driving since at first the wheels rotate and stop at the moment when the equilibrium-1 obtains:

The apparatus -may be constructed without any diifi'cul-ty so as to allow -of testing the brakes by either method *thisbeing usefu' lin the case;-

of very accurate measures.

What I claim and desire to secure by Letters Patent ofithe United Statesis: 7

- Apparatus for testingthe brakes of a vehicle by deter'miningthe value of the ratio' between the' brake'forc'e at-the rim of the wheel and f the weight 'supported by the wheel, comprising a movablesupport fcr -ea'oh wheel; abase having an incl ed cnrxdl'iriear -pathfioreach support, means for eil-ertihg a trac'tive iorce on'the br'aked wheel and ii ean's formeasuring the tangent of the le' formed between"the 'horizontal and a line drawn tangentially to'j the curvilinear path of the base, at the point of contachof-" the 'su-pportwi-th the said base when said support is in equilibrium with the tl aCtlVBIfC JZ-CGE 7 Apparatusror sun fbrakes offia motor vehicle comprisin bases-havi g'jiincl-i ned curvi linear paths,-carriagesf;or s-ifpp ting the heels of the vehicle on said path's'j means for 5111 ng the brakedvehi-cle and means ,measuringthe tangent of the angle formed betv'reerrthe-horizontal" and a line drawn tangentially to the-point 'of contacts? a-ca-iriage on the-curvilinear'paith of the"base-,when the carriage 'niovingion' this-base is-inequili-b m with thei -tractive force exerted h e??? R mai tei' s -i n. vehicle; comprisinginclined'curviiinear sui aces,

on Vthe braked wheel i-a idfof the weight of l said carriages for supporting ,the vehicle wheels'and resting on said inclined surf-aces, "counterweights for bringing said carriages to the top of said surfaces, releasable means for fastening them in this position,means for preventing horizontal movement of said vehicle'upon release of said carriages and means for'measuring the tangent of the angle formedbetween the horizontal and a line drawn tangentially to thecurvilinear sur-q face at the point of contact between the carriage and the surface when the carriages have come to rest. a I

4. An apparatus for testing the wheel brakes of a motor vehicle comprising, a movable carriage for each wheel, a surface on each carriage having a coeflicient of. friction withthe vehicle wheel at leastpequal to that of the average road-bed,

rollers on said carriages, said rollers being in,

contactwith stationary, inclined, curvilinear surfaces, 'means for. applying a continuous'tractive force to the braked vehicle mountedon the carriages, and means to indicate the position of the rollers on said curvilinear surfaces.

5. An apparatus for determiningthe value of the ratio of the brake force at the rim of a vehicle wheeland the weight supported by said wheel comprising four carriages placed in line by pairs,reach having a surface with a coefficient of friction with thevehicle wheel at least equal to that of the average road-bed, said carriages supportingothe four wheels of 'a'motor .vehicle, two inclined surfaces connected to said carriages for guiding the vehicle wheels onto the carriages, and two inclined surfaces .for guiding the vehicle from the carriages, rollers on said carriages, said rollers resting on stationary inclinedcurvilinear surfaces, a cylinder provided with a piston, movable under air pressure, means'for connecting said vehicle to said piston, and means to indicate the movements of said carriages ,upon movement of said piston. j

6. Apparatus for testing the brakes of a motor vehicle; comprising four carriages placed in'line ,7 by pairs, each having asurface with a coeiiicient of friction with the vehicle wheel at leastequal to that of the average road-bed, said carriages supporting the four wheels of a motor vehicle, rollers on said carriages, said: rollers resting on sta-' tionary, inclined, curvilinear surfaces, means for guiding the vehicle in moving it ont o'ancl from said carriages, means for applying a continuous .tractive forceonsaid vehicle, an indicator board including a casing-,;movable, indexes guided-in saiclcasing, means for connecting said indexes to the respective carriages,springs acting upon said indexes to move the sameupon movement-oi said carriages along their respective inclinedsurfaces and thereby indicate the position of; the carriages on said curvilinearsurfaceQ '7. An apparatus for testing the wheel brakes of a motor vehicle comprising a movable car- 7 riage for'each vehicle wheel, a surface on each carriage having a} coefficient of friction with the vehicle wheel at least equal to that of the average road-bed, means iorguiding the vehicle wheels onto and from their respective carriages, rollers on said carriages, Isaid rollers movable on stationary, inclined, curvilinear surfaces, a. cylinder provided with a piston movable under air pressure, means for'operatively connecting the piston to said vehicle, an indicator casing, movable indicator indexes guided in said casing, means for connecting said indexes to the respective carriages, said indexes being adapted to indicatethe position of said carriages with respect to said curvilinear surfaces.

. Apparatus for testing vehicle brakes by: de-

termining-ithe -value of the, ratio between the tangentialbrake force at the rim and the weight supported by the wheel, which'comprises a movablecarriage supporting each wheel, aninclined.

curvilinear pathway ior each carriage, means to exert a traction on; .the axle of the braked wheel,

and means for registering, the slope of the curvilinear pathway at the point where said carriage 'stopswhen it is in equilibrium under the actionof the;tractive,;force exerted on the axle of thebraked wheel and of the" weight of this wheel.- r 9. Apparatus for testing motor vehicle brakes for, successive brakeagevalues, which comprises inclined; curvilinear pathways, carriages I for supporting the whee1s,'these carriages being movable on said pathways, means for pulling the'braked vehicle, and means for determining the trigonometric tangent oi the angle made by the horizontal with a line drawn tangentially toeach rolling pathway at thestopping. point of the carriage when the latter is in equilibrium under the action of. a, tractive force exerted on thebraked 1 wheel determining thetrigonometric tangent, of the angle made with the horizontal by a line drawn tangentially to each curvilinear pathway at the stoppingpoint of the corresponding carriage on this pathway when the carriages have been freed.

. EMILE PIQUVEREEZ. 

